Most personal computers today utilize direct access storage devices (DASD) or rigid disk drives for data storage and retrieval. Present disk drives include a disk rotated at high speeds and a read/write head that, in industry parlance, xe2x80x9cfliesxe2x80x9d a microscopic distance above the disk surface. The disk includes a magnetic coating that is selectively magnetizable. As the head flies over the disk, it xe2x80x9cwritesxe2x80x9d information, that is, data, to the hard disk drive by selectively magnetizing small areas of the disk; in turn, the head xe2x80x9creadsxe2x80x9d the data written to the disk by sensing the previously written selective magnetizations. The read/write head is affixed to the drive by a suspension assembly and electrically connected to the drive electronics by an electrical interconnect. This structure (suspension, electrical interconnect, and read/write head) is commonly referred to in the industry as a Head Gimbal Assembly, or HGA.
More specifically, currently manufactured and sold read/write heads include an inductive write head and a magnetoresistive (MR) read head or element or a xe2x80x9cgiantxe2x80x9d magnetoresistive (GMR) read head to read data that is stored on the magnetic media of the disk. The write head writes data to the disk by converting an electric signal into a magnetic field and then applying the magnetic field to the disk to magnetize it. The MR or GMR read head xe2x80x9creadsxe2x80x9d the data on the disk as it flies above it by sensing the changes in the magnetization of the disk as changes in the voltage or current of a current passing through the MR or GMR head. This fluctuating voltage in turn is converted into data. The read/write head, along with a slider, is disposed at the distal end of an electrical interconnect/suspension assembly.
The suspension is essentially a stainless steel support structure that is secured to an armature in the disk drive. Typically, a suspension will include a base plate including a radius (or spring region), a load beam, and a flexure. The read/write head is attached to the tip of the suspension with adhesive or some other means. At least one tooling discontinuity may be included.
An interconnect may include a base or substrate, which may be a synthetic material such as a polyimide, that supports typically a plurality of electrical traces or leads of the interconnect. The electrical interconnect may also include a polymeric cover layer that encapsulates selected areas of the electrical traces or leads. The interconnect is terminated to bond pads on the read/write head and forms an electrical path between the drive electronics and the read and write elements in the read/write head.
As mentioned previously, the slider xe2x80x9cfliesxe2x80x9d only a microscopic distancexe2x80x94the xe2x80x9cfly heightxe2x80x9dxe2x80x94above the spinning media disk. Control of fly height is critical for the operation of a disk drive. If the fly height is too large, the read/write head will not be able to read or write data, and if it is to small, the slider can hit the media surface, or crash, resulting the permanent loss of stored data. As such, the fly height of the slider is determined in much part by the characteristics of the head suspension assembly to which it is mounted. The head suspension imparts a vertical load, commonly referred to as xe2x80x9cgram loadxe2x80x9d, on the slider, normal to the surface of the disk, in order to oppose the xe2x80x9cliftxe2x80x9d forces created by the air passing between the slider and the spinning disk. As a result, head suspension assemblies are manufactured with a very precise gram load, typically with a tolerance of xc2x10.2 grams. Another head suspension assembly characteristic that has a significant effect upon the fly height of a slider, is referred to as xe2x80x9cstatic attitudexe2x80x9d. Static attitude is the angular attitude of the gimbal to which the slider is mounted. Typically, head suspension assemblies are manufactured with tolerances for static attitude approaching xc2x130 arc-minutes.
Successful reading or writing of data between the head and the spinning media also requires that the head be precisely positioned directly above the location on the disk to which data is to be written or read. As such, great care is taken to design and manufacture head suspension assemblies so as to optimize the suspension""s vibrational, or resonant, performance.
There are three basic configurations of electrical interconnect/suspension assemblies that are currently utilized in the disk drive industry. With the first, a Trace Suspension Assembly, or TSA, the electrical interconnect is fabricated integrally with the flexure. The TSA flexure/interconnect is fabricated by selectively removing material from a laminate of stainless steel, polyimide, and copper. The TSA flexure/interconnect is then attached to a loadbeam, typically with one or more spot welds between the stainless steel layer of the TSA flexure/interconnect and the stainless steel of the loadbeam. Another interconnect configuration, termed CIS, is very similar to TSA in that the CIS interconnect is also fabricated integrally with the flexure. However, the CIS interconnect/flexure is fabricated with xe2x80x9cadditivexe2x80x9d processes, rather than xe2x80x9csubtractivexe2x80x9d processes. The CIS interconnect/flexure is attached to a load beam in much the same manner as the TSA flexures and conventional flexures are, with one or more spot welds between the stainless steel of the flexure and that of the loadbeam. The last interconnect configuration that is utilized today by disk drive assemblers is essentially a flexible circuit. The flexible circuit consists of a base polymer, typically a polyimide, which supports copper traces, or leads. In this case, the interconnect is fabricated independently from the flexure, and is later adhesively attached to a conventional head suspension assembly, to form a Flex Suspension Assembly, or FSA.
The attachment of conventional flexures to load beams with spot welds has been practiced for years throughout the head suspension industry and is well understood. Thus, the attachment of a CIS or TSA interconnect/flexure to a loadbeam utilizes existing techniques, and does not present any significant challenges for manufacturers of head suspension assemblies. On the other hand, adhesive attachment of flexible circuits to conventional head suspension assemblies results in a number of issues which the manufacturer of head suspension assemblies must address. An adequate amount of adhesive is required between the conventional head suspension assembly and the flexible circuit to ensure that the flexible circuit securely attached. However, adhesive that flows into the xe2x80x9cactivexe2x80x9d regions of the flexure or radius can compromise the head suspension assembly""s overall performance, specifically it""s gram load and static attitude attributes. Additionally, the amount of adhesive joining the flexible circuit to the head suspension assembly must be consistent from one FSA to another so as not to impart a significant amount of variation on the resonant performance of the FSA.
While FSA is significantly cheaper than it""s counterparts, namely TSA and CIS, the degradation in FSA performance due to the adhesive attachment of the flexible circuit creates a tradeoff between cost and performance that must be considered when comparing the competing technologies.
As such, it would be desirable to eliminate the degradation in FSA performance associated with the adhesive attachment of the flexible circuit to the head suspension assembly.
It is an object of the present invention to provide a method of adhesively attaching an electrical interconnect to a conventional head suspension assembly without significantly degrading the static attitude attributes of the head suspension assembly.
It is still another object of the present invention to provide a method of adhesively attaching an electrical interconnect to a conventional head suspension assembly without significantly imparting variation to the gram load attributes of the head suspension assembly.
It is yet another object of the present invention to provide a method of adhesively attaching an electrical interconnect to a conventional head suspension assembly without significantly affecting the dynamic resonance attributes of the head suspension assembly.
It is another object of the present invention to provide a method of adhesively attaching an electrical interconnect to a conventional head suspension assembly without significantly affecting the desired gimbal stiffness attributes of the head suspension assembly.
The foregoing objects are provided by the present invention, which is directed to a head suspension assembly that cantilevers a read/write magnetic transducer head adjacent the rotating surface of a disk in a disk drive from an actuator arm of the disk drive, and the method of constructing the head suspension assembly. The head suspension is disclosed in variant embodiments, all including adhesive control and distribution features designed to improve both the performance characteristics and manufacturing yields of head suspension assemblies with adhesively attached electrical interconnects.
Head suspension assemblies and electrical interconnects in accord with the present invention may include through-hole features and component perimeter overlays that impede the flow of adhesive into areas of the flex suspension assembly which may degrade the suspension assembly""s performance attributes.